1. Field of the Invention
The present invention relates generally to a fixture and process for use during evaluation of integrated circuits and other semiconductor devices. More particularly, it relates to a reusable carrier for temporarily holding a semiconductor device as an unpackaged die or as a chip-scale package while the semiconductor device is tested and/or burned in and to a burn-in and/or electrical test process using a reusable carrier.
2. Description of the Prior Art:
When fabrication of integrated circuits and other semiconductor devices, such as memory devices and discrete power transistors, has been completed, the semiconductor devices are subjected to burn-in and electrical test in order to identify and eliminate defective semiconductor devices before shipment to a customer. The term "burn-in" relates to a procedure in which the semiconductor devices are exercised at a controlled temperature, typically an elevated temperature in an oven, and certain operating electrical bias and/or signals are supplied to the semiconductor devices while they are at the elevated temperature. The use of the elevated temperature accelerates stress to which the devices are subjected during burn-in, so that marginal devices that would otherwise fail shortly after being placed in service fail during burn-in and are eliminated before shipping. In electrical test, a more complete set of operating bias and signals is supplied to the device to provide a thorough evaluation of its functions.
As presently practiced, both burn-in and complete electrical test are not carried out until the semiconductor devices have been assembled in packages as they will be inserted in circuit boards. For burn-in, the packaged devices are temporarily inserted in sockets of special burn-in boards which include circuit traces for contacting a sufficient number of contact pins or pads on the packages to provide the operating electrical bias and/or signals used during burn-in. In some burn-in applications, contact needs to be made only to a limited number of pins or pads of a packaged integrated circuit. For electrical test to verify performance, the integrated circuit is removed from the burn-in board and placed in a test fixture that will allow electrical contact to all of the pins or pads of the packaged integrated circuit.
When a packaged integrated circuit is found to be defective during burn-in or electrical test, it must be scrapped. In addition to the defective die, the integrated circuit package itself must be discarded. For many years, it has therefore been desired to carry out the testing and burn-in of integrated circuits at the die level, before being packaged. Also, the advent of multi-chip modules (MCMs) has led to a new requirement for actually shipping devices in die form for assembly of several die into an MCM. The die must be tested and burned in before assembly into the MCM, since MCMs are difficult and expensive to repair. While many proposals to do this have been made, they have not achieved general use. A significant factor preventing burn-in and/or electrical test at the die level has been the lack of a fixture for carrying and protecting the die during burn-in and/or electrical test that will meet the stringent requirements for such a carrier.
Additionally, the die may be packaged using chip-scale packaging, in which the package is only slightly larger than the die. In this case, the contacts are still very small, and the package follows the outline of the die, so standard sockets are not available for a device this small. Therefore, there is a need for a carrier for burning-in and testing chip-scale packaged dies.